Study Finds Summer Sunshine Boosts Fertility

A new study finds that women undergoing IVF who had been exposed to sunlight, higher temperatures and less rain the month before had a third higher pregnancy rates.

Study Finds Summer Sunshine Boosts Fertility Monkey Business Images/Shutterstock

The long days and gorgeous weather of summer may have you feeling frisky, and if you're trying to conceive, here's a new reason to go ahead and get it on now: A new study presented at a European fertility conference last week found that women undergoing fertility treatments who had been exposed to more sunlight, higher temperatures and less rain in the month before their IVF had over a third higher pregnancy rates.

Vitamin D is the key

Researchers at the University of Ghent in Belgium included more than 11,000 patients over the course of six years in the study, in order to determine if there was any pattern to when the most successes occurred. Surprisingly, the weather conditions in the month that the actual IVF cycle took place didn't matter—it was the month before when the scientists saw a pattern emerge. Dr. Frank Vandekerckhove, M.D., Ph.D., a reproductive medicine specialist at University Hospital Ghent, tells that even before conception, more sunshine increased pregnancy odds. "It probably had a positive effect on the quality of the oocytes [immature eggs] that were recruited in the weeks before ovarian stimulation started," he says.

Vandekerckhove speculates that the increase in sunlight boosts vitamin D and affects the level of the hormone melatonin, both of which have a role in regulating women's reproductive cycles. "These hormones are produced in larger amounts under the influence of light," he says. "That's why we think there is a correlation with our findings." Previous research has shown that vitamin D is a factor in successful pregnancy outcomes, improving egg quality and implantation rates. Melatonin helps our circadian rhythms and sleep patterns, but also helps control the timing of female menstrual cycles.

Could supplements mimic the sun's effects?

All this bodes well for summertime baby-making. But come fall and winter, could taking a vitamin D supplement increase fertility as well? Vandekerckhove declined to comment, citing a lack of data. Even so, because of the general prevalence of vitamin D deficiency you may benefit from taking a supplement, especially during the colder months when, depending on where you live, you often can't get enough from the sun. Once you become pregnant you are also advised to supplement, because low levels of vitamin D in pregnancy can increase the risk of preterm birth, infection, preeclampsia and poor bone development. Of course, check with a doctor before you start any supplementation.

This study looked specifically at pregnancy rates from IVF, but there's no reason to think that natural conceptions might not be likewise affected by the increased sun of summer. Vandekerckhove says that's "pure speculation" at this point, but still, it's a good excuse to have lots of sex. And given that another recent study pointed to men's sperm being twice as active in the summer months, now seems to be the best time all year to do the baby dance.